This unit is designed for Tamiya's 1/14 Scale R/C Tractor Truck Series models. The Semi-Trailer Light Set when combined with the Tractor Truck Electrical Unit Set (available separately), allows the modeler to further enhance appearance and performance with functional blinkers and brake lights. The unit can be easily installed on the semi-trailer without any complicated wire connecting chores. Power is supplied by the truck's running battery. The set includes semi-trailer connector cable with light bulbs and internal circuitry board connector cable. Includes easy to understand instructions